1. Field of the Invention
The present invention relates to a pattern recognition type optical memory device, a method for reading data from the memory, and a method for writing data to the memory.
2. Description of the Related Art
In a conventional method of processing data stored in a storage device using an atomic force microscope (AFM), a pattern formed on the surface of the storage device is detected using a probe formed on an extreme end of a micro cantilever. The cantilever is designed to flex up or down, even by applying only a minute force. The probe is suspended on the extreme end of the cantilever and has a size corresponding to several atoms. When the probe approaches the surface of a sample device, an attractive or repulsive force is generated between an atom of the probe and an atom of the surface of the sample according to a distance between the atoms. Data from the surface is detected by detecting the resulting force exerted on the probe.
IBM's Millipede is well known as a typical storage device which processes data using an AFM. The writing operation of the Millipede is performed by forming an indentation on a storage medium formed of poly-methyl methacrylate (PMMA). The indentation is formed by heat generated by a resistive heater embedded in a tip of the AFM.
The data written using the above writing operation is read by detecting a degree of flexure of the cantilever using a piezoresister when the tip of the cantilever scans the storage medium.
The quality of the data storage device, to or from which the data is written or read, depends on the density, speed and power consumption properties thereof. That is, it is important to design the data storage device with high-density, high-speed and low power.
However, when elements of the prior art data storage device are nanometer-sized, resolution problems occur, which make it difficult to detect the shape of a pattern. Also, there is a limitation in the size reduction of the elements due to a physical limitation in forming the pattern. Furthermore, when the data is processed using the cantilever, the data reading and writing cannot be performed during the time taken to move the cantilever to a next position to again perform the sensing or detecting operation.